Disc brakes

ABSTRACT

A spot-type disc brake has a fixed caliper straddling the disc and containing hydraulic actuator pistons acting on the back plates of opposed brake pads disposed at opposite sides of the disc. The back plates have &#39;&#39;&#39;&#39;T&#39;&#39;&#39;&#39; shaped side edge portions whose circumferentially inwardly facing surfaces cooperate with circumferentially outwardly facing abutment surfaces on the caliper. This enables the brake drag forces to be taken from the brake pads at their leading edges.

United States Patent Rath et al. 1 Jan. 2, 1973 [54] DISC BRAKES [56]References Cited [75] Inventors: Heinrich Bernhard Rath, Koblenz- UNTEDSTATES PATENTS Luetzel; Wolfgang Hess, Rubenach, b of Germany 3,162,27212/1964 Gancel ..188/73.3

[ Assigneei Girling Limited, Birmingham, Primary Examiner-George E. A.Halvosa gland Attorney-Scrivener, Parker, Scrivener and Clarke 22 F1 d:S t. 22, 1970 l 1 57 ABSTRACT [21] Appl' 74,328 A spot-type disc brakehas a fixed caliper straddling the disc and containing hydraulicactuator pistons act- [30] Foreign Application Priority Data ing on theback plates of opposed brake pads disposed at opposite sides of thedisc. The back plates have T Sept. 25, 1969 Great Britain ..47,135/69Shaped Side g portions whose circumferentiany wardly facing surfacescooperate with circumfi F' g "188/ ferentially outwardly facing abutmentsurfaces on the 1 nt. v calipen This enables the brake drag forces to betaken [58] Field of Search ..188/73.1, 250 B, 72.4, 72.5, from the brakepads at their leading edges.

10 Claims, 6 Drawing Figures 10 2s -II 15 32 3.2 38 Q L 38 34 U 34 K 131 S I w 9 1 i l 3 39 Q) 33 PATENTEDJM 2 I975 SHEET 2 [IF 4 PATENTEU M2W 3.70 8 043 sum u 0F 4 DISC BRAKES The present invention relates tospot-type disc brakes having a caliper adapted to straddle the disc anda pair of opposed brake pads located in the caliper and adapted to beurged against opposite faces of the disc by actuator means.

In accordance with the invention the brake drag forces are taken fromthe brake pads at the leading edges thereof.

Thus the present invention provides a spot-type disc brake in whichcircumferentially outwardly facing abutment surfaces are provided on acaliper member and/or on some other member which is fixed and each brakepad assembly is provided with complementary, circumferentially inwardlyfacing surfaces for cooperation with the outward abutment surfaces forthe purposes of taking the brake drag forces from the pad assemblies.

Preferably, for each pad assembly the abutment surfaces on the caliperor other member include an abutment surface disposed radially outwardlyof the line of action of the brake drag force and an abutment surfacedisposed radially inwardly of this line of action.

The invention is advantageously applicable to a fixed caliper disc brakein which the caliper may have a closed top. Thus the actuating means cancomprise opposed pistons slidable in bores in opposite limbs of thefixed caliper.

The invention is further described, by way of example, with reference tothe accompanying drawings in which:

FIG. 1 is a side elevation viewed in the direction of the arrows I inFIG. 2 and 4 of a spot type disc brake constructed in accordance withone embodiment of the invention,

FIG. 2 is a sectional elevation on the line II-II of FIG. 1,

FIG. 3 is a sectional view on the line III--III of FIG.

FIG. 4 is a plan view partly sectioned on the line IV- IV of FIGS. 2 and3,

FIG. 5 is a side elevation, partly sectioned on the line V-V of FIG. 6,of a second embodiment of disc brake, and

FIG. 6 is a view on the line VI--VI of FIG. 5.

Referring first to FIGS. 1 to 4, a spot-type disc brake has a fixedcaliper 10 having a closed top or bridge part 11. The caliper 10comprises two caliper members 12 and 13 secured to one another by bolts14 passing through holes in the top part of the member 12 and screwedinto screw-threaded bores 15 in the top part of the member 13. Thecaliper member 12 has mounting ears 16 which enable the caliper to besecured so that it straddles a disc 17.

Each caliper member 12, 13 contains a blind bore or cylinder l8, 19 inwhich slides a piston 20, 21 of hydraulic actuating means. Each piston20, 21 bears against the back plate 22, 23 of a respective pad assembly24, 25 and serves to press the friction pad 26, 27 against therespective face of the disc 17. The inner ends of the blind bores 18 and19 are interconnected by a passage 28 which is formed through the bridgepart 11 and to which a bleeder orifice 29 is connected. A brake fluidinlet 30 is connected to the base of the blind bore 18.

As can be seen in FIG. 2 particularly, the back plate 22 of the padassembly 24 as T shaped side edge portions 31. Flat mutually facingsurfaces 32 of the radially outward limbs of the T shaped side edgeportions .31 bear on complementary, abutment surfaces 34 and 35 formedon the caliper l0 and facing away from one another. Likewise, flatmutually facing surfaces 33 of the radially inward limbs of the sideedge portions bear on complementary abutment surfaces 35 formed on thecaliper l0 and facing away from one another. More specifically theabutment surfaces 34 which are located radially outwardly of the line 36of action of the brake drag force developed at the friction pad 26 areformed on the caliper member 12 on the bridge part thereof. The abutmentsurfaces 35 which also face away from one another are formed on lugs 37which are integral with the caliper member 12. The surfaces 32 and 33 onthe pad assembly 24 are perpendicular to the line 36 of action and thepad assembly 24 is radially located by flat locating surfaces 38 and 39which are parallel to the line 36 of action and cooperate with theradially outward and inward ends of the T shaped edge portions 31, theouter surfaces 38 being disposed on the bridge part of the member 12 andthe surfaces 39 being formed on the lugs 37.

Whilst FIG. 2 shows the pad assembly 24 it will be appreciated that thepad assembly 25 is of identical construction and cooperates withidentical abutment and locating surfaces of which the radially innersurfaces 35 and 39 are formed on lugs 40 integral with the calipermember 13 and the radially outer surfaces 34 and 38 are formed on thebridge part of the caliper member 13.

If it is assumed now that the normal direction os rotation of the disc17 is clockwise as seen in FIG. 2 and as indicated by the arrow 41, thebrake drag forces developed at the friction pads 26 and 27 aretransferred to the fixed caliper 10 at the left hand abutment surfaces32 and 33 (FIG. 2). Since the abutment surfaces 32 and 33 are atopposite sides of the line 36 of action of the frictional forces noresultant couples are applied to the pad assemblies, 24 and 25 whichwould tend to turn these pad assemblies. In fact, the provision for thebrake drag forces to be taken from the pad assembly at the leading edgesthereof leads to greater stability of the pad assemblies since they arebeing pulled rather than pushed in contrast to known pad assemblies,wherein the brake drag forces are taken at the trailing edges. Thisfeature may also lead to reduced tendency for brake squeal to takeplace. The provision of T shaped edge portions 31 on both edges of thepad assemblies enables the same brake to be used for disc rotation ineither direction.

Other features are that manufacture is simplified since the abutmentsurfaces are exterior surfaces of the caliper and are therefore easierto machine and that it is possible to construct the brake with a greaterpad area thereby resulting in longer pad life.

FIGS. 5 and 6 of the drawings show another embodiment which is in manyrespects similar to the embodiment of FIGS. 1 to 4 and like parts aredenoted by like reference numerals. The principal difference is that theradial locating surfaces 38 and 39 on the caliper 10' are omitted andinstead the pad assemblies 24' and 25' are radially located by centralprojections 42 formed on the pistons and 21 and projecting into centralapertures 43 formed in the pad back plates 22 and 23.

Whilst the drawings illustrate only one piston on each side of the discit is possible to provide two pistons side by side at each side of thedisc such that both pistons on either side act on a common pad assembly.

We claim:

1. A spot-type disc brake comprising a caliper adapted to straddle adisc rotatable about a rotary axis, a pair of opposed brake padassemblies located in the caliper, each pad assembly having a back plateand a brake pad thereon, actuator means adapted to urge the brake padsof the pad assemblies against opposite faces of the disc, and means forsustaining brake drag forces from the leading side only of said padassemblies considering the rotation of said disc, said last named meanscomprising first and second radially spaced pairs of circumferentiallyspaced abutment surfaces on each of said back plates, said pairs beingon the radially outer and inner sides respectively of the line of actionof the braking drag force acting on the respective pads when the latterare urged against a rotating disc, the abutment surfaces of each pairmutually facing inwardly, a non-rotatable drag force sustaining memberhaving first and second parts spaced apart axially with respect to therotating axis of the disc, first and second separate pairs ofcircumferentially spaced abutment surfaces disposed on each of the partsof the drag force sustaining member on the radially outer and innersides respectively of said line of action, the abutment surfaces of eachpair mutually facing outwardly and being complementary to andcooperating with the respective first and second pairs of abutmentsurfaces on the respective back plates, said cooperating abutmentssustaining the braking forces at the leading side of said pad assemblyon both sides of the line of action of the braking forces throughout thelife of the pads.

2. A disc brake according to claim 1 in which said abutment surfaces areflat and are perpendicular to said line of action.

3. A disc brake according to claim 1 in which the drag force sustainingmember comprises portions of said caliper.

4. A disc brake according to claim 3 in which said caliper comprises afixed caliper.

5. A disc brake according to claim 4 in which said actuator meanscomprise cylinders in opposite limbs of said caliper and pistonsslidable in said cylinders.

6. A disc brake according to claim 5 in which said pad assemblies haverecesses therein and said pistons have projections thereon extendinginto said recesses to radially locate said pad assemblies.

7. The spot-type disc brake of claim 1 wherein each back plate has sideedge portions disposed circumferentially of its brake pad, said firstand second pairs of abutment surfaces extending radially outwardly andinwardly respectively from said side edge portions.

8. The disc brake of claim 7 in which said side edge portions areT-shaped, said abutment surfaces being defined by the inner faces of thelimbs of the T-shaped parts of said side edge portions.

9. A disc brake according to claim 8 in which the abutment surfaces onsaid non-rotatable drag sustaining member include radially inwardly andoutwardly facin locatin surfaces constru ted and arran ed to coopratewit the extremities of said limbs of s aid T- shaped side edge portionsto radially locate said pad assemblies.

10. A disc brake according to claim 9 in which the radially inwardly andoutwardly facing surfaces on the extremities of said limbs are parallelto said line of action and cooperate with said locating surfaces.

1. A spot-type disc brake comprising a caliper adapted to straddle adisc rotatable about a rotary axis, a pair of opposed brake padassemblies located in the caliper, each pad assembly having a back plateand a brake pad thereon, actuator means adapTed to urge the brake padsof the pad assemblies against opposite faces of the disc, and means forsustaining brake drag forces from the leading side only of said padassemblies considering the rotation of said disc, said last named meanscomprising first and second radially spaced pairs of circumferentiallyspaced abutment surfaces on each of said back plates, said pairs beingon the radially outer and inner sides respectively of the line of actionof the braking drag force acting on the respective pads when the latterare urged against a rotating disc, the abutment surfaces of each pairmutually facing inwardly, a non-rotatable drag force sustaining memberhaving first and second parts spaced apart axially with respect to therotating axis of the disc, first and second separate pairs ofcircumferentially spaced abutment surfaces disposed on each of the partsof the drag force sustaining member on the radially outer and innersides respectively of said line of action, the abutment surfaces of eachpair mutually facing outwardly and being complementary to andcooperating with the respective first and second pairs of abutmentsurfaces on the respective back plates, said cooperating abutmentssustaining the braking forces at the leading side of said pad assemblyon both sides of the line of action of the braking forces throughout thelife of the pads.
 2. A disc brake according to claim 1 in which saidabutment surfaces are flat and are perpendicular to said line of action.3. A disc brake according to claim 1 in which the drag force sustainingmember comprises portions of said caliper.
 4. A disc brake according toclaim 3 in which said caliper comprises a fixed caliper.
 5. A disc brakeaccording to claim 4 in which said actuator means comprise cylinders inopposite limbs of said caliper and pistons slidable in said cylinders.6. A disc brake according to claim 5 in which said pad assemblies haverecesses therein and said pistons have projections thereon extendinginto said recesses to radially locate said pad assemblies.
 7. Thespot-type disc brake of claim 1 wherein each back plate has side edgeportions disposed circumferentially of its brake pad, said first andsecond pairs of abutment surfaces extending radially outwardly andinwardly respectively from said side edge portions.
 8. The disc brake ofclaim 7 in which said side edge portions are T-shaped, said abutmentsurfaces being defined by the inner faces of the limbs of the T-shapedparts of said side edge portions.
 9. A disc brake according to claim 8in which the abutment surfaces on said non-rotatable drag sustainingmember include radially inwardly and outwardly facing locating surfacesconstructed and arranged to cooperate with the extremities of said limbsof said T-shaped side edge portions to radially locate said padassemblies.
 10. A disc brake according to claim 9 in which the radiallyinwardly and outwardly facing surfaces on the extremities of said limbsare parallel to said line of action and cooperate with said locatingsurfaces.